core: window: implement get_window_info()

This commit implements a method for getting platform specific window
information from Kivy window providers.

Platform specific window system information is useful for
programatically acquiring a handle to the Kivy window.

When unable to retrieve windowing subsystem information, the function
returns `None`. Currently, only the SDL2 window provider actually
implements the function, using SDL_GetWindowWMInfo. The implementation
only returns information for Linux (X11/Wayland) and Windows.

kivy/core/window/__init__.py

@@ -131,6 +131,9 @@ def __init__(self, **kwargs):
         #: VKeyboard widget, if allowed by the configuration
         self.widget = kwargs.get('widget', None)
 
+    def get_window_info():
+        pass
+
     def on_key_down(self, keycode, text, modifiers):
         pass
 

kivy/core/window/_window_sdl2.pyx

@@ -10,6 +10,12 @@ from kivy.graphics.cgl import cgl_get_backend_name
 
 from cpython.mem cimport PyMem_Malloc, PyMem_Realloc, PyMem_Free
 
+IF UNAME_SYSNAME == 'Linux':
+    from window_info cimport WindowInfoX11, WindowInfoWayland
+
+IF UNAME_SYSNAME == 'Windows':
+    from window_info cimport WindowInfoWindows
+
 cdef int _event_filter(void *userdata, SDL_Event *event) with gil:
     return (<_WindowSDL2Storage>userdata).cb_event_filter(event)
 
@@ -333,6 +339,38 @@ cdef class _WindowSDL2Storage:
     def set_window_pos(self, x, y):
         SDL_SetWindowPosition(self.win, x, y)
 
+    def get_window_info(self):
+        cdef SDL_SysWMinfo wm_info
+        SDL_GetVersion(&wm_info.version)
+        cdef SDL_bool success = SDL_GetWindowWMInfo(self.win, &wm_info)
+
+        if not success:
+            return
+
+        IF UNAME_SYSNAME == 'Linux':
+            cdef WindowInfoWayland wayland_info
+            cdef WindowInfoX11 x11_info
+
+            if wm_info.subsystem == SDL_SYSWM_TYPE.SDL_SYSWM_WAYLAND:
+                wayland_info = WindowInfoWayland()
+                wayland_info.display = wm_info.info.wl.display
+                wayland_info.surface = wm_info.info.wl.surface
+                wayland_info.shell_surface = wm_info.info.wl.shell_surface
+                return wayland_info
+            elif wm_info.subsystem == SDL_SYSWM_TYPE.SDL_SYSWM_X11:
+                x11_info = WindowInfoX11()
+                x11_info.display = wm_info.info.x11.display
+                x11_info.window = wm_info.info.x11.window
+                return x11_info
+        IF UNAME_SYSNAME == 'Windows':
+            cdef WindowInfoWindows windows_info
+
+            if wm_info.subsystem == SDL_SYSWM_TYPE.SDL_SYSWM_WINDOWS:
+                windows_info = WindowInfoWindows()
+                windows_info.hwnd = wm_info.info.win.hwnd
+                windows_info.hdc = wm_info.info.win.hdc
+                windows_info.hinstance = wm_info.info.win.hinstance
+
     # Transparent Window background
     def is_window_shaped(self):
         return SDL_IsShapedWindow(self.win)

kivy/core/window/window_info.pxd

@@ -0,0 +1,19 @@
+include 'window_attrs.pxi'
+
+from libc.stdint cimport uintptr_t
+
+IF UNAME_SYSNAME == 'Linux':
+    cdef class WindowInfoWayland:
+        cdef wl_display *display
+        cdef wl_surface *surface
+        cdef wl_shell_surface *shell_surface
+
+    cdef class WindowInfoX11:
+        cdef Display *display
+        cdef Window window
+
+IF UNAME_SYSNAME == 'Windows':
+    cdef class WindowInfoWindows:
+        cdef HWND hwnd
+        cdef HDC hdc
+        cdef HINSTANCE hinstance

kivy/core/window/window_info.pyx

@@ -0,0 +1,37 @@
+IF UNAME_SYSNAME == 'Linux':
+    cdef class WindowInfoWayland:
+        @property
+        def display(self):
+            return <uintptr_t>self.display
+
+        @property
+        def surface(self):
+            return <uintptr_t>self.surface
+
+        @property
+        def shell_surface(self):
+            return <uintptr_t>self.shell_surface
+
+
+    cdef class WindowInfoX11:
+        @property
+        def display(self):
+            return <uintptr_t>self.display
+
+        @property
+        def window(self):
+            return <uintptr_t>self.window
+
+IF UNAME_SYSNAME == 'Windows':
+    cdef class WindowInfoWindows:
+        @property
+        def hwnd(self):
+            return <uintptr_t>self.hwnd
+
+        @property
+        def hdc(self):
+            return <uintptr_t>self.hdc
+
+        @property
+        def hinstance(self):
+            return <uintptr_t>self.hinstance

kivy/core/window/window_sdl2.py

@@ -188,6 +188,9 @@ def __init__(self, **kwargs):
 
         self.bind(allow_screensaver=self._set_allow_screensaver)
 
+    def get_window_info(self):
+        return self._win.get_window_info()
+
     def _set_minimum_size(self, *args):
         minimum_width = self.minimum_width
         minimum_height = self.minimum_height

setup.py

@@ -779,6 +779,7 @@ def determine_sdl2():
     'graphics/cgl_backend/cgl_sdl2.pyx': merge(base_flags, gl_flags_base),
     'graphics/cgl_backend/cgl_debug.pyx': merge(base_flags, gl_flags_base),
     'core/text/text_layout.pyx': base_flags,
+    'core/window/window_info.pyx': base_flags,
     'graphics/tesselator.pyx': merge(base_flags, {
         'include_dirs': ['kivy/lib/libtess2/Include'],
         'c_depends': [
@@ -1021,6 +1022,8 @@ def get_extensions_from_sources(sources):
             '*.pxi',
             'core/text/*.pxd',
             'core/text/*.pxi',
+            'core/window/*.pxi',
+            'core/window/*.pxd',
             'graphics/*.pxd',
             'graphics/*.pxi',
             'graphics/*.h',